Smoking raises type 2 diabetes risk even after quitting

By David Liu

Cigarette smoking is a known risk factor for type 2 diabetes. But a new study found that the increased risk could be seen years after smokers gave up the habit.

The study led by researchers at the Johns Hopkins University School of Medicine found those who quit smoking were at 70 percent increased risk of developing type 2 diabetes in the first six years after cessation of their smoking habits compared to those who did not smoke.

The researchers found that study participants tended to gain weight after quitting smoking cigarettes, which they believe may be the cause for the increased risk of type 2 diabetes.

Hsin-Chieh "Jessica" Yeh, Ph.D. co-authers and colleagues, cautioned that smokers should not use the findings as an excuse to continue smoking, which increases risk for lung disease, heart disease, stroke and cancer.

Dr. Hsin-Chieh advised in a statement released by John Hopkins that if you don't smoke, don't even start to smoke and if you do, quit smoking and watch your weight.

The study published in the Jan 5 issue of Annals of Internal Medicine involved 10,892 middle-aged men and women who were free of diabetes when they were enrolled in the study between 1987 and 1989.

The participants were followed for up to 17 years and data on diabetes status, blood sugar, weight and other health parameters were collected regularly.

The researchers found the risk of diabetes was highest in the first three years after quitting, but it became normal 10 years later compared to those who did not smoke.  At the end of the study, the risk was still 30 percent higher than that for those who never smoked.

A health observer cautioned warned that the findings can be misleading.  He suggested that it is meaningless to compare quitters to non-smokers.

Type 2 diabetes affects an estimated 20 million men and women in the United States.  Patients with this disease often can produce insulin, the hormone that is needed for blood sugar metabolism, but can't use the hormone effectively.

Diabetes can lead serious consequences like blindness, kidney failure, nerve damage and heart disease.

It has been known that overweight people are at higher risk of developing type 2 diabetes.  In the study, during the first three years, the quitters gained about 8.4 pounds.

However, the press release by John Hopkins did not say how much weight the non-smokers gained during the 17-year follow-up.  Other studies have found obesity and overweight have been on the rise steadily so the non-smokers might also increase their body weight. This means that it remains unknown whether weight gain is a cause for the increased diabetes risk.

It is possible, according to the health observer who did not want to be named, that what the researchers observed were simply the consequences resulting from the former smoking.  The study did not seem to have compared the quitters to the non-quitters for their risks of diabetes.  And it is possible that the non-quitters may have experienced an even higher risk during the study.

Smoking has been associated with increased risk for type 2 diabetes, according to a review published in the Dec 12 2007 issue of Journal of American Medical Association.

Carole Willi, M.D., of the University of Lausanne, Switzerland, and colleagues, authors of the review, found associations between active smoking and the incidence of diabetes or other glucose metabolism irregularities.

The review of 25 studies published between 1992 and 2006 which followed a total of 1.2 million participants for 5 to 30 years, found active smokers were at a 44 percent increased risk of type 2 diabetes compared to non-smokers.

The researchers were able to quantify a dose response relationship between smoking and diabetes. They found heavy smokers were at a 61 percent increased risk and lighter smokers at a 29 percent increased risk.

They found the former smokers were 23 presently less likely to develop diabetes compared to the active smokers.

Vitamin D has also been associated with vitamin D deficiency, according to Dr. John Cannell, direcotr of Vitamin D Council.  Those who want to reduce the risk may consider taking high doses of this sunshine vitamin D.

Diet is also important.  Trans fat has been associated with increased risk of diabetes.